And, you normally get namespace collisions if you try and have more than one sheet called the same thing. Using spaces is a workaround, and is not immediately obvious. Wonder how long it will take people to realise just how I managed to get several sheets called the same thing in one document.

Yeah, there's a software engineering principle that basically says "Don't name things ALMOST EXACTLY the same, differing only by upper/lowercase, or by adding/subtracting underscores, because this becomes a maintenance nightmare."

There are exceptions to this rule -- in C++, conventions say a Class starts with an uppercase character, but instantiated objects of that Class (variables, in other words) should start with a lower-case letter. Or is that Java?

Anyway, adding/removing spaces to make virtually identical, yet separate names, is not recommended either. But I guess you're finding that out by experience.

I had a better one. The users didn't like their leading zeros stripped when the .CSV file was double clicked, and they didn't want to format the columns. So, I concatenated the 0xA0 character to the beginning of the number and voila! the leading zeros remained, and everybody was happy.